the Lender. As a result, we recorded a gain from forgiveness of our notes payable of approximately $0.4 million for the nine months ended September 30, 2021.
Sublease income. On January 5, 2022, we executed a four-month sublease agreement for certain laboratory space at our Holliston, Massachusetts facility. For the nine months ended September 30, 2022, we recorded sublease income of approximately $0.1 million relating to this agreement.
Grant income
For the nine months ended September 30, 2022 and 2021, we recorded grant income of approximately $0 and $0.2 million, respectively, for qualified expenditures under our SBIR grant which expired effective September 30, 2021.
Other (expense) income, net
The warrants classified as a liability expired unexercised during the nine months ended September 30, 2022 and the remaining liability on the expiration date of approximately $2,000 was recognized as other income. During the nine months ended September 30, 2021, the change in fair value of our warrant liability resulted in other expense of approximately $14,000 due primarily to a higher stock price of the underlying common shares.
During the nine months ended September 30, 2022, we recorded interest expense of approximately $7,000 for on insurance installment payments. During the nine months ended September 30, 2021, we received a refund payment of approximately $0.1 million for certain withholding taxes paid in previous years to the German tax authorities which were remitted on to us on behalf of Harvard Apparatus Regenerative Technology GmbH, our German subsidiary.
Liquidity and Capital Resources
Sources of liquidity. We have incurred operating losses since inception, and as of September 30, 2022, we had an accumulated deficit of approximately $81.5 million. We are currently investing significant resources in the development and commercialization of our product candidates for use by clinicians and researchers in the fields of regenerative medicine and bioengineering. As a result, we expect to incur operating losses and negative operating cash flows for the foreseeable future.
The following table sets forth the primary uses of cash for the nine months ended September 30, 2022 and 2021 (in thousands):
| | | | | | |
| | Nine Months Ended September 30, |
| | 2022 | | 2021 |
Net cash used in operating activities | | $ | (3,373) | | $ | (1,627) |
Net cash used by investing activities | | $ | (8) | | $ | — |
Net cash provided by financing activities | | $ | 5,060 | | $ | 2,596 |
Comparison of Nine months Ended September 30, 2022 and 2021
Operating activities. Net cash used in operating activities of approximately $3.4 million for the nine months ended September 30, 2022 was due primarily to our net loss of approximately $4.6 million and an increase of $0.3 million for financing costs offset by adjustments for non-cash items of approximately $0.8 million due to non-cash expenses for share-based compensation and depreciation, and an approximately $.7 million increase to cash from changes in working capital due to the timing of payments for accounts payable, accrued expenses and prepaid expenses.
Net cash used in operating activities of approximately $1.6 million for the nine months ended September 30, 2021 was due primarily to our net loss of approximately $2.1 million and adjustments for non-cash items of approximately $0.1 million due to the add-back for a gain from forgiveness of our notes payable, offset, in part, by non-cash expenses including share-based compensation, depreciation and the change in fair value of our warrant liability. These cash outflows were offset, in part, by an approximately $0.4 million increase to cash from changes in working capital due to the timing of payments for prepaid expenses and accounts payable.
Investing activities. Net cashed used in investing activities for the nine months ended September 30, 2022 and 2021 totaled approximately $8,000 and zero, respectively, and represented purchases of property, plant and equipment.